Expanded code in CompareCSSValuePtr to be more readable
Expanded code in CompareCSSValuePtr to be more readable

Expanded the ternary operator in CSSValuePtr to a set of if-statements
that are much more readable. This code was previously difficult to
understand and this change should not noticeably affect performance
(this code is not part of a performance-critical path).

For more info, see this doc:
https://docs.google.com/document/d/1srJG5_Obcmty8NlsTNMJiYhVZlMdmzASWJHPnIQNB0I/edit

Review URL: https://codereview.chromium.org/1194073002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@197496 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk